Masao Ohkuchi

Synthesis and bioactivities of novel pyridazine derivatives: inhibitors of interleukin-1 beta (IL-1β) production

New pyridazine derivatives were prepared, and their abilities to inhibit IL-1beta production were evaluated. Some compounds showed potent inhibitory activity against IL-1beta production in HL-60 cells stimulated with lipopolysaccharide (LPS). The synthesis and structure-activity relationships of these compounds are described.

Synthesis and bioactivities of novel 5,6-bis(4-methoxyphenyl)2H-pyridazin-3-one derivatives : Inhibitors of interleukin-1 beta (IL-1β) production

New 5,6-bis(4-methoxyphenyl)-2H-pyridazin-3-one derivatives were prepared, and their abilities to inhibit IL-1beta production were evaluated. Some compounds showed potent inhibitory activity against IL-1beta production in HL-60 cells stimulated with lipopolysaccharide (LPS). The synthesis and structure-activity relationships of these compounds are described.

The glycosylation sites and structural characteristics of oligosaccharides on recombinant human thrombomodulin.

Thrombomodulin (TM) is an anticoagulant glycoprotein on the surface of endothelial cell that directly inhibits the procoagulant activities of thrombin, and the TM-thrombin complex accelerates thrombin-catalyzed activation of protein C. Soluble TM in urine has no glycosaminoglycan (GAG) chain which accelerates the anticoagulant activities. Therefore, we expressed recombinant GAG-modified urinary thrombomodulin (GAG-UTM) in C127 cells. The glycosylation sites were determined by amino acid sequence analysis of peptides digested with trypsin after S-carboxymethylation. The structures of N-linked oligosaccharides were estimated by two-dimensional sugar mapping of pyridylaminated oligosaccharides that were treated with exoglycosidase. The disaccharide composition analysis of the GAG chain was performed by HPLC using digestion with chondroitinase ABC, ACII and B. Consequently, it was revealed that the N-linked oligosaccharides were assigned to Asn29, Asn98, Asn364, Asn391; those structures were estimated biantennary, 2-6 branched triantennary and 2-4 branched triantennary complex type oligosaccharides that were linked by fucose at the ratio of 1.0:0.5:0.1, respectively. Moreover, the attachment site of the GAG chain was assigned to Ser472. It was then estimated that the GAG chain contained chondroitin-4-sulfate and dermatan sulfate, which were repeated approximately 30 times. In this paper, the GAG attachment site and structural characteristics of GAG-UTM, were confirmed. Moreover, structures of the N-linked oligosaccharides of GAG-UTM are described for the first time.

Characterization of immunoreactive endothelin in human urine

We developed three antibodies, specific and sensitive to endothelin-1 (ET-1), and established two sandwich and three competitive enzyme immunoassays (EIAs). By using these EIAs, large immunoreactive ET (IR-ET) of molecular weight 10 k Da was identified as a main component of IR-ETs in human urine. This large IR-ET, which reacted with two antibodies specific for N-terminal region of ET-1 but not with the antibody against C-terminal peptide of ET-1, was partially purified by six-step procedure and examined by Western blotting after SDS polyacrylamide gel electrophoresis. The large IR-ET was detected as a single band at molecular weight of 10 k Da both in reduced and non-reduced conditions. From these results, the large IR-ET was thought to consist of a single polypeptide chain and possess the steric restricted N-terminal region of ET-1.

Pyrogenic action of endothelin in conscious rabbit

Injection of 0.3 nmol/kg endothelin(ET)-1 into the ear vein of conscious rabbits induced a significant increase in body temperature. ETB receptor specific agonist, namely 4-Ala-ET-1, also caused an elevation of the body temperature in a dose-dependent manner by injection into the ear vein of rabbit. These results suggest that ET play important roles in regulation of body temperature through selective stimulation of ETB receptor.

Protein C activation by recombinant thrombomodulin in plasma

Recombinant glycosaminoglycan-modified urinary thrombomodulin (GAG-UTM), which partially improved the amino acid sequence of human urinary thrombomodulin (UTM), was expressed in C127 cells. GAG-UTM accelerates protein C activation by thrombin and also thrombin inhibition by antithrombin III (ATIII) in the buffer system. Both accelerating activities of GAG-UTM are more potent than those of unmodified recombinant UTM (r-UTM) without a GAG chain. As ATIII in plasma also inhibits protein C activation by a thrombin-thrombomodulin complex, we studied whether GAG-UTM accelerates protein C activation in plasma. GAG-UTM suppressed the generation of thrombin in activating plasma protein C stronger than r-UTM. By Western blot analysis using anti-protein C antibody, activated protein C was generated by GAG-UTM more than by r-UTM. From these results, the acceleration of activated protein C formation by GAG-UTM was confirmed in plasma too.